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Question #46219
The Question
A biennial dicot plant with a modified storage taproot undergoes extensive secondary growth during its vegetative phase. If it experiences an abrupt, severe drought during its reproductive phase, the mobilization of stored reserves to the developing inflorescence is severely hindered. Which of the following anatomical and physiological events primarily explains this systemic failure?
Options
- A.
Cavitation in the secondary xylem vessel elements breaks the continuous hydraulic column, preventing the upward translocation of mobilized resources.
- B.
The vascular cambium ceases activity, preventing the formation of autumn wood and halting the active transport of sucrose through the xylem.
- C.
Suberization of the endodermal Casparian strips completely blocks the symplastic movement of water from the storage parenchyma to the stele.
- D.
The secondary phloem sieve tube elements collapse due to high negative hydrostatic pressure, halting bidirectional transport.
Check Your Answer
Correct Answer
Step-by-Step Solution
Explanation
How the Examiner Thinks
Regulatory_Failure
Understand how NOT, EXCEPT, and logical constraints are used to manipulate exam results.
Concepts Behind This Question
Root_Modifications|Spring_vs_Autumn_Wood|Stele_Definition
Why This Question Is Tricky
Common Mistakes
Conceptual Pivot: This question tests the integration of Root Anatomy (secondary growth) and Plant Physiology (transport).
Students often forget that extensive secondary growth in roots destroys the endodermis, rendering Casparian strip logic invalid (Option C).
Furthermore, it tests the fundamental difference in pressure dynamics: xylem operates under negative tension (prone to cavitation), while phloem operates under positive pressure (Option D trap).
Quick Facts About This Question
Question Information
| Subject | Biology |
| Chapter | Morphology of Flowering Plants - Class 11 |
| Concept | Root Modifications |
| Difficulty | 8 |
| Cognitive Load | 5 |
| Target Solve Time | 120 sec |
| Access | Free |